Method for the construction of concrete shafts for a platform or similar structure and a section for similar use

ABSTRACT

Procedure for the construction of a concrete shaft for a platform or similar structure, where one of several of the shafts will be outfitted with relatively much equipment. The shafts are constructed of prefabricated sections which are consecutively installed butt-in-butt on top of each other and which are left in the shaft as an internal fully shaped shaft component, as the sections internally contain associated equipment and externally feature bodies for the installation of easily removable formwork elements, preferably easily mountable slipforms, while the space between the formwork elements and a prefabricated section is filled with reinforcement and concrete. The formwork elements, after the hardening of poured concrete, by a per se known procedure, are moved to a higher level.

The present invention relates to a method for the construction ofconcrete shafts for a platform or similar structure which may forinstance rest on the seabed, where one or several shafts will beoutfitted with relatively much equipment.

The present invention in addition relates to a section to be used as aninternal formwork and/or stiffening for the construction of a concreteshaft in a platform or similar structure which may for instance rest onthe seabed.

So far, it has been common to use traditional slipforming for theconstruction of a platform or similar structure. This means that theshaft must first be constructed in its full height, and any outfittingin the shaft must be subsequently performed. Thus, considerable work andtime will be spent on the outfitting of the shafts with said equipmentafter the completed casting of the shafts. This gives substantialadditional construction cost.

By outfitting the individual concrete shaft of the said type with thenecessary equipment simultaneously with the casting of the shafts, thepresent invention is intended to reduce the required construction timeand thus also the costs. In other words, the intention, at least for theshafts to be outfitted with equipment, is to construct the shafts in anew way, while other shafts, if any, are constructed by means oftraditional slipforming. It should be observed that the advantages ofthe invention increase with the depth of the water.

The new construction method according to the invention is characterizedby the shafts of the said type being constructed of prefabricatedsections which are consecutively installed butt-in-butt on top of eachother and which are left in the shaft as an internally fully shapedshaft component, as the sections internally contain the associatedequipment and externally feature bodies for mounting of easily removableformwork elements or attachments for slip-forming. The sections eitherserve as internal formwork where the external formwork is subsequentlyinstalled, or alternatively, as an attachment for internal formwork asthey are built up by means of tubulars on which the internal andexternal formworks are attached. The space between the formworks isfilled with reinforcement and concrete, by a per se known procedure, andis thus moved up to a higher level.

According to the invention, the advantage of this is that said sectionsmay be built in heights of 15-20 m, which may in their turn be puttogether to form longer sections onshore prior to being transferred tothe platform. The sections which form the internal formwork orattachment for the internal formwork may be prefabricated on anappropriate construction site with associated equipment completelyinstalled in sections, in an easily accessible way on an appropriateinstallation site - and said sections may later be consecutivelyinstalled in the shaft, which is under construction, in a relativelysimple and accurate way. The easily accessible section provides acorrespondingly effective installation of the equipment in eachindividual section. In addition, a particularly rational installation ofthe equipment in the different sections is provided, as the sections canbe constructed and outfitted with equipment independently of theconstruction of the actual shaft.

As soon as one section has been installed in the shaft, which is underconstruction, this part of the shaft has simultaneously beenprefabricated internally, and the different sections can subsequently beconsecutively attached on top of each other and the shaft can beprefabricated internally, as the shaft is gradually constructed.Consequently, when the casting of the shaft is completed, the shaft willsimultaneously be fully outfitted internally. Thus, the total time spenton the platform construction or similar structure can to a considerableextent be reduced by a corresponding reduction of the otherwise normaltime spent on the outfitting of shafts.

A section according to the invention is characterized by comprising acylindrically shaped section with a diameter for instance of 10 to 40 mof steel sheet, or alternatively being built up of tubular elements,which internally feature one or several horizontal dividers for supportof the equipment to be installed in the shaft and which externallyfeature stiffening bodies, at least some of these being adjusted to forman attachment for easily mountable and easily dismountable formworkelements, by said dividers and said stiffening bodies being adjusted tostiffen the section during the transportation of the same from theconstruction site to the place of installation and being part of theconstructed concrete shaft.

In addition to the reduction of time required for the construction ofthe platform or similar structure, installation-related advantages areobtained, as already mentioned, as there is a better accessibility tothe section and different individual sections respectively than to anextended shaft. In connection with the previously employed slipforming,it was necessary to construct special horizontal dividers at variouslevels directly in the actual shaft followed by the installation of theequipment on the different horizontal dividers. By the presentinvention, where said dividers are built directly into the associatedsegment and where the segments can be assembled and joined togetherbutt-in-butt to form a continuous structure internally in the shaft,there will be labour-related (assembly-related) and construction-relatedadvantages. By installing the equipment in a section, the assembly workcan be limited to said butt-in-butt assembly and joining together of thesections in relation to one another during the construction of thesections in the shaft. Moreover, by means of the horizontal divider orthe horizontal dividers in each section, an effective extra stiffeningis obtained for the section during the transportation of the same fromthe construction site to the installation site, i.e. during thetransportation directly to the assembly in the shaft which is underconstruction.

Further characteristics of the invention will appear from the subsequentdescription with reference to the enclosed drawings, which show thepreferred embodiments, of which:

FIG. 1 is a horizontal sectional view of a section according to theinvention for use during the construction of a concrete shaft in aplatform which may for instance rest on the seabed.

FIG. 2 is a vertical sectional view of a section according to FIG. 1.

FIG. 3 is a horizontal sectional view corresponding to FIG. 1, thesection featuring external formwork elements.

FIG. 4 is a vertical sectional view corresponding to the section in FIG.2 featuring external formwork elements, shown during ;the constructionof the external formwork.

FIG. 5 is a vertical sectional view of the lower foundation withassociated storage cells and the lower part of a shaft according to theinvention, shown during the casting.

FIG. 6 is an alternative embodiment by the section being built up of atubular element on which internal and external formworks have beeninstalled.

FIGS. 1-4 generally show the mounting of the formwork for a shaft wherea platform or other concrete structure may for instance rest on theseabed.

FIG. 5 shows the actual construction of the shaft 10 in connection witha foundation 11 which may for instance rest on the seabed through alower base-plate (13). The shaft 10 rests directly on the base-platethrough a tubular lower shaft section 10a, said shaft may be constructedby a per se known procedure in a rigid connection with cells (14) spacedaround the circumference, said cells being adjusted to form tanks forballast and/or for storage of oil or condensate produced from theseabed. After the cells 14 and the lower shaft part 10a have beenprefabricated by a per se known procedure in a continuous piece with thebase-plate 13, the further construction of the shaft continues by a newprocedure according to the invention, as described below. Alternatively,the lower shaft part (10a) or parts of the same may be constructed inthe same way as the rest of the shaft (10), this is particularlyrelevant if the lower shaft part contains much equipment.

A separate section 15 is subsequently constructed, corresponding to thatshown in FIGS. 1 and 2, on an appropriate construction site separatedfrom the construction site of the actual shaft. The section 15 generallyconsists of a cylindrical steel sheet 16 (e.g. with a thickness of 25mm) and a number of horizontal dividers 17. On the different dividers17, the relevant equipment is pre-installed as indicated by broken lines18, and a flight of stairs 19 is indicated between the dividers 17. Inaddition, hatches may be installed (not further shown) for coverage ofthe upper end of the flight of stairs and hatches (not further shown)for vertical transportation of equipment between the different stories.In the illustrated embodiment, a section is shown which may comprise arandomly chosen number of story heights, but evidently, when desirable,each section may have only a few or even one single story height.

In the embodiment shown in FIG. 1 (and FIG. 3), a schematic location isshown of four equipment components on one horizontal divider 17, eachcomponent being located right above an associated beam section 20a, 20b,20c, 20d in a cruciform beam structure 20, which forms a stiffening foreach story divider In FIG. 2, it is indicated that the beam structure 20is supported by angle pieces 21 for stiffening of the beam structure 20internally of the tube 16.

Externally, the section 15 features an annular horizontal stiffeningbody 22 (only shown in FIGS. 1-3) at the section's upper free end.Alternatively, several such horizontal mutually parallel stiffeningbodies may be installed at various levels in the vertical direction onthe tube. Moreover, vertical stiffening bodies 23 have been weldedexternally of the tube which have a T- shaped cross-section with atypical T-shape dimension of 0.1 m in the full vertical direction of thesection. The different sections may for instance be joined togetherbutt-in-butt by means of a continuous annular weld and may in additionbe mutually connected through welds by mutually aligned verticalstiffening bodies 23.

By designing the vertical stiffening bodies in a T-shape according tothe invention, with the T-shape's cross piece turned radially outward,appropriate anchoring bodies 24 may be effectively anchored to theinternal formwork formed by the sections 15, for clamping of externalformwork elements 25 to the internal formwork, as shown in FIGS. 3 and4. Bow-shaped anchoring bodies 24 are shown, which are threaded intoplace on the stiffening bodies 23 and are somewhat radially extendedoutside the same for support of the formwork elements 25 at a suitabledistance radially outside the internal formwork. The bow-shapedanchoring bodies 24 may for instance, as illustrated, feature outwardlyextended support surfaces endwise, as mounting bolts 26 may beintroduced through corresponding holes in the formwork elements forattachment in threaded fastening holes in said support surfaces Theformwork elements 25 may moreover be connected sideways in pairs bymeans of mounting bolts 27 with associated retaining screws 28introduced through fastening holes in radially outwardly facing flangeson the formwork elements 25.

According to the embodiment shown in FIG. 3, sixteen stiffening bodies23 are shown, but only eight of these are used for attachment of theformwork elements.

According to FIG. 5, an embodiment is shown where the casting of a firstsection 15' in the shaft is practically completed, while a secondsection 15" is installed over the section 15', ready for the mounting ofexternal formwork elements. On the fully cast part of the shaft, i.e. inthe illustrated embodiment on the part which contains section 15', anannular work platform 30 is attached which may rest against the shaftthrough pairs of rollers 32 on diametrically oppositely facing sides ofthe shaft. The work platform 30 may be attached to the shaft throughbrake bodies 33 at the inner end of skewed downwardly and inwardlyturned support arms 34. In addition, the work platform may be supportedthrough support wires 35 attached to the top of the upper section--inthe illustrated embodiment, the top of section 15". From the workplatform, the joining together may be done butt-in-butt with theabutting sections and parts connected to these, including theinstallation of the external formwork elements, as the shaft is beingconstructed in the vertical direction As the shaft is gradually cast andhardened, the formwork elements are moved, e.g. by the completelyhardened shaft parts being slid upward for installation on a sectionabove, and when this is completely or more or less completely cast, theformwork is moved further upward, and the process is subsequentlycontinued in a corresponding way to the top of the shaft. When the shafthas been constructed in full height, the associated equipment in theshaft has been correspondingly installed at the respective levels alongthe shaft.

FIG. 6 shows an alternative way of installing formwork elements on thesections which contain equipment 18. The sections are built up ofhorizontal 41 and vertical 42 tubes respectively On the vertical tubes,T-shaped stiffening bodies 43 are installed with the T-shape's crosspiece turned radially outward, on which appropriate anchoring bodies 44may be effectively anchored for the internal formwork 45. The externalformwork 46 may be attached to the internal formwork with stiffeners 47and the formworks may be screwed together with mounting bolts 48, 49with associated retaining nuts 50 introduced through the fastening holesin the radially outwardly turned flanges on the formwork elements 45 and46.

We claim:
 1. The method of constructing a concrete shaft or similarstructure for receiving equipment, comprising:a) consecutivelyinstalling a plurality of prefabricated shaft component sections inn anend-to-end relationship, the sections including a plurality of externalstiffening bodies; b) attaching formwork elements to the externalstiffening bodies at a first level; c) filling a space between theformwork elements and the sections with concrete; and d) moving theformwork to a second level.
 2. The method according to claim 1, furthercomprising a supporting equipment internally on the sections.
 3. Themethod according too claim 1, further comprising:a) casting a shaftsection in a foundation with a plurality of associated cells encasingthe shaft, the shaft being located in a platform for storage of oil, theplatform being installed with equipment; and b) installing the sectionsconsecutively in the shaft section.
 4. The method according to claim 3,including resting the platform on a seabed.
 5. A prefabricated shaftcomponent section for use in the construction of a concrete shaft in aplatform, comprising:a) a cylindrical steel sheet having a plurality ofhorizontal dividers for supporting equipment; and b) a means forstiffening the sections during transportation and construction includinga plurality of stiffening bodies, at least some of the bodies includingadjustable means for attaching a plurality of formwork elements thereto.6. A prefabricated section according to claim 5, wherein at least someof the stiffening bodies comprise vertical bodies, the bodies extendingvertically outwardly from the section and being T-shaped with anexternal cross-piece of the T forming a plurality of attachment bodies.7. A prefabricated section according to claim 6, wherein the attachmentbodies are radially outwardly extending clamping rings for theattachment of a plurality of external formwork elements by means ofmounting bolts or the like.
 8. A prefabricated shaft component sectionaccording to claim 5, wherein the platform rests on a seabed.
 9. Aprefabricated shaft component section for use in the construction of aconcrete shaft in a platform comprising:a) a plurality of steel tubes,the tubes being welded together horizontally and being welded verticallyto a tubular lattice framework; b) at least one horizontal dividerlocated inside the tubes for supporting equipment; and c) a means forstiffening the sections during transportation and construction,including a plurality of external stiffening bodies, at least some ofthe bodies including adjustable means for attaching a plurality offormwork elements thereto.
 10. A prefabricated shaft component sectionaccording to claim 9, wherein the platform rests on a seabed.